/Engine/Source/Runtime/AnimationCore/Public/BoneWeights.h
Set the number of elements to reserve in the container. The elements can be left in an uninitialized state. TheTBoneWeightsalgorithms will ensure that all elements will be properly defined at the end of an operation.
static void SetNum ( [ContainerType](API\Runtime\AnimationCore\FBoneWeightNullAdapter\ContainerType) & InContainer, int32 InNum )